Functional resins have heretofore been used for imparting functions such as gas-barrier properties and the like properties to the biaxially stretch blow-molded containers. For example, there have been proposed a variety of multi-layer containers including inner and outer layers of a polyester resin such as polyethylene terephthalate and an intermediate layer of a resin composition comprising a gas-barrier resin such as ethylene/vinyl alcohol copolymer or a polyamide resin, an oxidizing organic component and a transition metal catalyst.
Referring to the container comprising a polyester resin, on the other hand, it is a modern trend to recycle the containers. From this point of view, therefore, it is desired that the container as a whole comprises the polyester resin and, therefore, not to use resins or resin compositions other than the polyester resin. It is, therefore, desired that in the multi-layer containers, too, the functional resin or the resin composition that forms the intermediate layer is the polyester resin.
A polytrimethylene naphthalate has also been known as a functional polyester resin having excellent heat resistance, gas barrier property and, particularly, carbon dioxide gas-barrier property. There have been, further, proposed a polyester multi-layer sheet having a polyethylene terephthalate resin layer and a polytrimethylene naphthalate resin layer (patent documents 1, 2) and a single-layer bottle comprising a blend of an ethylene terephthalate type polyester resin, a polybutylene naphthalate and a polytrimethylene naphthalate (patent document 3).
That is, the polytrimethylene naphthalate type polyester resin is a polyester resin having thermal properties close to those of the polyethylene terephthalate and, further, has excellent gas-barrier property offering superior heat moldability to that of other kinds of gas-barrier resins that have heretofore been used being laminated on the polyethylene terephthalate. Besides, the polytrimethylene naphthalate type polyester resin is the polyester resin which is the same as the polyethylene terephthalate. Therefore, the multi-layer container thereof also using the polyethylene terephthalate is suited to being excellently recycled.                Patent document 1: JP-A-2000-296593        Patent document 2: JP-A-2001-038866        Patent document 3: European Patent Application Laid-Open No. 1650260        